I have had a reply from NTS.

They make it clear that the wearing of the Sgian Dubh is not illegal but that they, as organisers, have decided to ban it after consulting with the Police. I think Downunder identified this in post#23.

I have replied accepting that everyone wants the event to be safe. I go on to say that they are targeting the risk from one group of attendees while ignoring the risk from irresponsible or drunken attendees with bottles. I finish by saying that the NTS do not appear to be discharging their duty of care in a proper and balance way and that I will not be renewing my membership.

I do not think that I can influence this further.

Peter